ISO Calculator

Find the ISO that closes the exposure triangle for your EV, aperture and shutter. Live updates.

Inputs

Target EV

Aperture (f-number)

Shutter (seconds)

Press Calculate to update results as you change values.

Results

When ISO is the free variable

Lock aperture for depth of field and shutter for motion, then raise ISO until the exposure matches your target EV. This calculator returns the numeric ISO that satisfies the equation so you can set the camera or judge whether the noise level will be acceptable.

Formula

ISO = 100 × 2^( log₂(N²/t) − EV )

Example

EV 12, f/2.8, 1/100 s → ISO ≈ 50 (below many cameras’ base—meaning the scene is bright enough to stop down or speed up the shutter instead).

FAQ

Is higher ISO always worse?

Higher ISO amplifies noise. Modern full-frame cameras often remain usable past ISO 6400; smaller sensors show noise earlier. Prefer base ISO when light allows.

What about dual native ISO?

Some cinema and hybrid bodies have two native ISO points with clean performance. Use the higher native ISO when you would otherwise push a noisy mid-range setting.

ISO strategy

Treat base ISO as the default for maximum dynamic range. When aperture and shutter are already fixed by depth of field and motion, this calculator tells you how far ISO must climb. On dual-native-ISO cinema cameras, jump to the higher native setting when the math lands near it, rather than lingering in a noisy mid-range. Always confirm with a test frame: algorithms and highlight recovery vary by body, so the numeric ISO is a plan, not a guarantee of identical noise.